This invention relates generally to safety equipment for school busses and more particularly to a crossing arm assembly configured to mount on the front end of a school bus.
School bus crossing arms are designed to extend to a perpendicular position relative to a front bus bumper when a school bus stops to pick up or discharge passengers. In this perpendicular position, such a crossing arm will block arriving and departing passengers from crossing immediately in front of a school bus and below the bus drivers field of vision. U.S. Pat. No. 5,357,239, granted to me Oct. 18, 1994, shows such a crossing arm assembly, or xe2x80x9csafety gate,xe2x80x9d that comprises a hollow or solid bar attached at one end to a plastic bracket. The plastic bracket is configured to pivotally mount the bar on a housing.
Others have attempted to provide improved crossing arm arrangements. For instance, U.S. Pat. No. 4,697,541 granted Oct. 6, 1987 to James H. Wicker discloses a crossing arm unit that comprises a short pivot plate. The pivot plate is made of a sturdy, relatively heavy gage metal (e.g. 3.5 in. of 14-gauge steel), a longer support plate of relatively light gauge metal (e.g. 20 in. of 0.08-in. aluminum plate) and a long U-shaped rod (e.g. 4 ft. of xc2xc-in. aluminum rod). The U-shaped rod serves as a pedestrian barrier.
According to the Wicker patent specification the crossing arm unit is light in weight to avoid structural problems with its support. The unit is easily supported, is simple to construct and is economical to manufacture. The Wicker patent, at column 1, also states that crossing arms have been made of lightweight fiber glass rods and that the Wicker construction improves on these prior art constructions.
However, the Wicker construction is unduly complicated particularly when its assembly requirements are taken into account. Moreover, the long U-shaped rod is fragile, deforms easily and is prone to plastic rather than elastic deformation. The U-shaped rod also requires a strut that further complicates and adds to the expense of the Wicker construction. Furthermore, the U-shaped rod has a narrow profile and is not highly visible. U.S. Pat. No. 5,199,754 granted Apr. 6, 1993 to Lowell J. D. Freeman discloses crossing arm or barrier whose construction includes tubular fiberglass. While the Freeman crossing arm construction is simple in comparison to the Wicker construction, it includes only a single rod that is heavy and rigid.
U.S. Pat. No. 3,153,398, granted Oct. 20, 1964 to George LaVerne Runkle and Gilbert S. Sheets, discloses a crossing arm structure that comprises a channel-shaped section of light sheet metal. The channel-shaped section is stiffened by a U-section having out-turned legs fixed to the back of the channel shaped section. The crossing arm assembly is shaped to fit in a recess in the front bumper of a bus. The assembly also includes a rubber guard structure that has a hollow rectangular center portion that is cemented to the channel section and flange portions that seal off the bumper recess.
This crossing arm structure is unduly complicated and expensive to manufacture. Furthermore the arrangement requires a hinge structure to attach the crossing arm to the bumper. This hinge structure further complicates construction and adds expense.
All the above designs have crossing arms that are cantilevered, i.e., supported by and extending rigidly from only one end. Therefore, a person applying force near the free distal end of any of these arms has a tremendous mechanical advantage over the mechanisms associated with the support and can damage the support or permanently bend or break the arm. If not securely latched to the front of the bus, the inertia of the arm can cause it to swing forward from the bus, uncommanded, whenever the bus decelerates. In addition, an arm supported in this manner is prone to sagging under its own weight. Arm weight can also make it difficult to dampen oscillations that occur when arm rotation is stopped abruptly in the perpendicular extended position.
Therefore, what is needed is a crossing arm that is less massive and therefore has less momentum to cause it to swing forward whenever its host bus stops or slows in traffic. What is also needed is a crossing arm that resists sagging, is configured to withstand considerable abuse, e.g., hinge damage that can result when force is applied along the length of the arm, and is economical to manufacture.
In accordance with this invention a crossing arm assembly is provided that includes a mass-tapered cantilevered beam. The assembly attaches to a support at the front end of a bus to block pedestrian traffic from crossing immediately in from of the bus when the bus is stopped. The crossing arm assembly comprises a combined pivot/bracket that is pivotally attachable to the support. The combined pivot/bracket also includes a beam-mounting portion. The elongated cantilevered beam has a length extending between a beam inner end and a beam outer end. The beam is supported at the beam inner end on the beam-mounting portion of the combined pivot/bracket. The beam is generally mass tapered along the beam length from the beam inner end to the beam outer end. The mass taper concentrates beam mass closer to the support to reduce the tendency of the beam to sag under its own weight and/or to swing forward as the bus decelerates.
According to another aspect of the invention, the cantilever beam is flexible. Cantilever beam flexibility may also increase as a function of beam length as measured from the beam inner end toward the beam outer end. Beam flexibility prevents loads applied near the beam outer end from damaging the support or plastically (permanently) deforming the beam.
According to another aspect of the invention, the beam is tapered in cross-sectional area from the inner end to the outer end. The taper increases flexibility and reduces mass at the beam outer end. The taper obviates the need to construct the beam using a support plate or webbing between two separate parallel rods. The tapered configuration of the beam is sufficiently strong to prevent sagging without using two rods with an interconnecting plate or web.
According to another aspect of the invention, the beam includes a first elongated rod. The first rod has a rod length that extends between a rod butt end adjacent the beam inner end and a rod tip end adjacent the beam outer end. The butt end of the first rod is connected to the beam-mounting portion of the combined pivot/bracket. The rod provides structural support for the beam.
According to another aspect of the invention, the first rod is mass tapered from the butt end to the tip end. The mass taper of the rod concentrates rod mass closer to the beam inner end and the support. This helps reduce beam sag and the tendency for the beam to swing forward.
According to another aspect of the invention, the first rod is tapered in cross-sectional area from the butt end to the tip end. This helps improve flexibility and reduce mass at the tip end of the first rod.
According to another aspect of the invention, the first rod is hollow and has a closed geometric cross section. The hollow construction significantly reduces rod mass.
According to another aspect of the invention, the first rod has an elongated generally frusto-conical shape that is relatively easy and inexpensive to manufacture and provides an aerodynamic profile that presents very little wind resistance.
According to another aspect of the invention, the first rod comprises flexible strips wound in a spiral pattern along the length of the rod. The spiral or helical application of the strips provides strength and flexibility.
According to another aspect of the invention, the first rod comprises a hollow fishing rod body. Fishing rod bodies are commercially available in great quantity and at low cost.
According to another aspect of the invention, a flap is pivotally attached to the first rod. The flap makes the beam highly visible yet provides little wind resistance. This reduces the problem of xe2x80x9cwind sailingxe2x80x9d that occurs when wind gusts hamper the operation of a crossing arm or cause the and to move, uncommanded.
According to another aspect of the invention, the flap comprises a flap panel disposed below and extending radially downward from and parallel to the first rod. The flap panel may comprise rigid material such as plastic and/or flexible material such as fabric.
According to another aspect of the invention, the flap comprises a flap pivot tube integrally connected along the flap panel upper edge, the flap tube having first and second opposite openings, and a portion of the first rod is disposed within the tube. The tube provides a simple engagement structure for pivotally suspending the flap from the first rod. Annular plugs may be concentrically disposed in the flap tube openings to compensate for rod taper.
According to another aspect of the invention, a second elongated rod may be attached at a butt end of the second rod to the beam-mounting portion of the combined pivot/bracket. The second rod is disposed generally parallel to and spaced below the first rod. A crosspiece may be connected between the tip of the first rod and a tip of the second rod. The resulting structure provides greater beam strength and visibility.
According to another aspect of the invention, the combined pivot/bracket includes two opposing pivot structures that are supported coaxially opposite each other on inner ends of respective upper and lower pivot arms of a U-shaped body. A vertical beam integrally connects outer ends of the pivot arms and a rod-mounting boss extends integrally outward from an outer end surface of the beam. At least one rod receptacle is formed in an outer end surface of the rod-mounting boss and the first rod butt end is disposed coaxially within the receptacle. This combined pivot/bracket construction is easy to manufacture and provides strong, low profile support to the rods and flap.